BUG/MEDIUM: hlua: Report to SC when output data are blocked on a lua socket

It is a fix similar to the previous one ("BUG/MEDIUM: hlua: Report to SC
when data were consumed on a lua socket"), but for the write side. The
writer must notify the cosocket it needs more space in the request buffer to
produce more data by calling sc_need_room(). Otherwise, there is nothing to
prevent to wake the cosocket applet up again and again.

This patch must be backported as far as 2.8, and maybe to 2.6 too.

src/hlua.c

@@ -3232,6 +3232,7 @@ hlua_socket_write_yield_return:
 		WILL_LJMP(luaL_error(L, "out of memory"));
 	}
 	xref_unlock(&socket->xref, peer);
+	sc_need_room(sc, channel_recv_max(&s->req) + 1);
 	MAY_LJMP(hlua_yieldk(L, 0, 0, hlua_socket_write_yield, TICK_ETERNITY, 0));
 	return 0;
 }